The present invention relates to a machine tool and a parameter adjustment method therefor, and particularly relates to a parameter adjustment system of a control system for a servomotor enabling adjustment in accordance with a load state of a drive section.
Machine tools, such as a lathe, use a servomotor for a drive system. The servomotor for a spindle or the like with a workpiece chucked is controlled to rotate.
Such a servomotor may be controlled with a method employing a closed-loop position control system, a closed-loop speed control system, and the like. The closed-loop position control system issues a drive command to the servomotor, in such a manner as to achieve an extremely small difference between a rotational position command issued from a controller, a driver, or the like and rotational position information detected by the servomotor. The closed-loop speed control system issues a drive command to the servomotor in such a manner as to achieve an extremely small difference between rotation speed information obtained by differentiating the rotational position information and a rotational speed command issued from the controller, the driver, or the like.
In the control systems, control system parameters, such as a parameter for gain adjustment, need to be adjusted in accordance with a load state.
The adjustment of various parameters requires expert knowledge and skills. Insufficient adjustment of the parameters results in vibrations, chattering on a machined surface of a workpiece, or the like.
A method for easily adjusting a parameter of the servomotor has been called for, especially for machine tools, such as a lathe, requiring a chuck for a spindle to be exchanged in accordance with the shape, the size, and the like of a workpiece, resulting in a large change in load-side inertia.
JP-A-H6-319284 discloses an apparatus and a method for adjusting a control parameter of a servomotor. Unfortunately, the invention according to this patent document, which is directed to achieving the adjustment with a single control parameter, is insufficient for a large change in load-side inertia.